مشخصات پژوهش

Abstract INTRODUCTION Wastewaters are rich in nitrate and phosphorus that contribute to health and environmental threats as they are linked to illnesses as well as ecosystem disruption. Microalgae are able to convert nutrients (nitrogen and phosphorus) from wastewater into biomass and bio-products, because they provide a bio treatment coupled with the production of potentially valuable biomass, which can be used for several purposes. Several microalgae could be used for this goal such as Chlorella, Neochloris and Dunaliella. Dunaliella salina is a unicellular halophyte alga that can be tested for optimizing condition for nitrate and phosphate removing. METHODS In order to evaluate the effectiveness of D. salina green algae in removing nitrate and phosphate from the culture medium, a culture medium containing (2, 3 and 4M NaCl) used in different light intensities (200, 600 and 1000 µmol photon m-2s-1) and different temperatures (25, 30 and 35°C), and was performed with 3 replications. Treatments named 200/30/3 A, 600/25/3B, 600/30/4C, 600/30/2D, 600/35/3E and 1000/30/3F. Initially amount of nitrate was 375 ppm and phosphate was 60 ppm (sufficient for normal D. salina culturing). During the growth period, the concentration of nitrate and phosphate was recorded at 0, 1, 7 and 14 days. Cells were counted in 14th days. RESULTS The results showed that only algae grown in 600/30/2D were able to delete nitrate about 70% (Fig. 1) and phosphate about 55% (Fig. 2). In such a situation, the number of D. salina cells was more than 2.5 times of the initial (Fig. 3). DISCUSSION According to the results of this study, it seems that this alga can be used to remove phosphates and nitrates, as well as the production of algal biomass in municipal wastewater treatment systems before entering the natural environment. Optimum condition for the best deletion of nitrate and phosphate was moderate light and temperature but low salinity led to maximum absorption and growth. Thus, D. salina ca